I don't know how Amazon does it. I just ordered diapers again for 30% off and free delivery. That means I got a giant pack of Pampers Swaddlers Sensitive, 132 diapers for $28, including free 2-day shipping. That's 22 cents each for premium toddler-sized diapers. Signed up for delivery again in a few months but I'll just cancel it if we don't need it then. Amazon mom is the best deal on disposable diapers right now.